Transient Analysis of Electrochemical Noise for 316 and Duplex 2205 Stainless Steels Under Pitting Corrosion

The use of electrochemical noise (EN) technique for the investigation and monitoring of corrosion has allowed many interesting advances in the corrosion science in recent years. A special advantage of EN measurements includes the possibility to detect and analyses the early stages of localized corrosion. However, the understanding of the electrochemical information included in the EN signal is actually very limited. This work shows the results obtained from EN measurements for different materials that exhibit pitting corrosion. The obtained transients in potential and current time, correlates with the scanning electron microscopy (SEM) surface analysis. Electrochemical measurements were made at different exposure times in order to obtain any correlation. The used materials were austenitic 316 stainless steel and 2205 duplex alloy, immersed in ferric chloride (FeCl3) and sodium chloride (NaCl) electrolytes. SEM analysis shows that the observed transients in the time series really correspond to the activity of pit nucleation developed on the surface of the electrodes.